Method of and apparatus for air conditioning



Aug. 24, '1943. G. 1E] ons 2,327,664

METHOD OF AND APPARATUS FOR AIR CONDITIONING f Gera/d E. Offs Aug. 24,1943. G. ET ons 2,327,664

METI'IIOD 0F AND 'APPARATUS FOR AIR CONDITIONING Filed Deo. 6, 1940 2Sheets-Sheet 2 /Z FE1-z Z CJP 5 Gem/c7 .E 0775 Patented Aug. 24, 1943UNITED STATES PATENTJOFFICE lvIETHOD F AND APPARATUS FOR AIR 1CONDITIONING Gerald E. Otis, Moline, Ill., assignor to The Herman NelsonCorporation, Moline, Ill., a corporation of Illinois ApplicationDecember 6, 1940, Serial No. 368,764

2 Claims.

The present invention relates in general to air conditioning and isconcerned more particularly with an improved method and apparatus for byit is possible to maintain an agreeable and wholesome atmosphere undervarying weatherv `greater part of the United States and in many othercountries, outdoor air may be satisfactorily used for cooling and isthev principal medium employed in this invention.- In schools and othercrowded spaces to which my invention is particularly adaptable, ltheindependent heating effect of occupancy usually tends to create anindoor temperature considerably higher than the outdoor temperature, andartificial cooling may be effected by introducing and diffusing outsideair in the space concerned. As will readily be appreciated by thoseskilled in the art, the outdoor air introduced may be precooled, Washedor otherwise treated, if desired, before entering the distributingapparatus illustrated, withoutA affecting the method of this invention.It is therefore evident that at the time I applied for this patentIforesawfurther utility of the method thereof, through the use ofpreconditioned air, and as will hereinafter appear, I have now devised amethod and means for providing preconditioned air in such a way as toextend the utility of the method and apparatus of my above patent toyear-round service under all weather conditions in a much more eicientand practical manner than heretofore employed.

The pronounced advantage of. Patent No. 1,913,681 lies in graduation ofthe outdoor air supply according to the actual duty imposed inmaintaining a fixed thermal status of the air in the space served. Asavingof more than fty percent in fuel consumption, over earlierconventional practice, was thus made possible in certain classes ofheating and Ventilating work such, for example, as in the large andimportant schoolhouse eld where it is now in general use. The potency ofthis feature in this particular is conditioning the air of roomsin'buildings wherea comparatively large quantity of fresh air.

limited to the heating season, but were this.' its only advantage, thebenefit during this period would, of course, be of great value inlyearround service. v Y

However, this feature has other advantages which are effective in summeras well as in winter conditioning service, and which take on an addedvalue in year-round service. One of these is that gaduation of' amixture of recirculated room air and cooler fresh air affords a simple,effective and reliable method of regulating the room temperature; and itis one which averts the danger of waste incurred by other methodsthrough adverse functioning of the heating and cooling means in thetransitional stage between heatingv and cooling duty. Another advantagelies in better humidity regulation throughout the year.

As pointed out in my earlier patent, the method thereof provides verylittle fresh air in cold weather, but increases the supply as theweather moderates. Since the moisture bearing capacity of air is limitedby its temperature,v it follows that air normally contains much lessmoisture in cold weather than in mild' or warm weather, Hence, in coldweather, when the room air would otherwise tend to be quite dry, themoisture content is allowed to build up under the effects of occupancy,because little fresh air is circulated, whereas in mild weather, whenthe air naturally contains sufcent moisture, the effect of occupancy isnullied by circulating In this Way the room humidity is kept Withinsatisfactory limits throughout the heating season. And, where precooledair is used for summer conditioning, this feature is of special value inguarding against excessive humidity. To illus- Itrate, suppose theapparatus be designed to maintain a room temperature of 80 F. in warmweather, in a room where the circulation rate is 30 cu. ft. per minuteper occupant and the duty requires that the air be introduced at F. Ifall the air introduced were preconditioned to 60 F., the relativehumidity of the room would rise to 55%; but, if a mixture of one partrecirculated air at F, and two parts of air preconditioned to 50 F. beused to obtain the required 60 F. mean, the relative humidity would bereduced to LLZ1/2%, which is a much better level. Moreover, under thismethod, the relative humidity will not vary so much under different loadconditions and will be more in line with that maintained during theheating season.

i' While the present invention broadens the utilratus of a capacity toity vof my patented method by providing improved means for supplyingprecooled air in accordance with the requirements of said method forsummer cooling and year-around service, it also constitutes animprovement in heating and Ventilating (winter) service- A commondifficulty in thermally conditioning rooms, under the normal range hofWeather conditions prevailing in the greater part of the country duringthe 4late fall, winter and early spring, is that appameet severeconditions is hard to regulate smoothly in average 'and mild weather;and failure to do so is liable to result in drafty room conditions.Through the present invention, the work is divided into steps whichserve to overcome this difficulty.

Although the present invention is in the main directed to improvementsin the method and apparatus of my United States Letters Patent No.1,913,681, it is to be distinctly understood that I do not propose tothus limit its application, since it will be appreciated by thoseskilled in the art that the invention is susceptible of wide and generaluse.

Other objects and features of the invention will more fully appear fromthe following detailed description taken inconnection with theaccompanying drawings, which illustrate a preferred I embodimentthereof, and in which:

Figure 1 is a combined vertical sectional view through a building floorand diagrammatically representing the arrangement of the apparatus ofthe 4present invention for carrying out my improved method ofconditioning the room thereof; and

Figure 2 is an enlarged vertical sectional view taken throughanindividual room-conditioning unit of a type adapted for utilization inconnection with the present invention.

As shown on the drawings:

As shown in Figure 1, a room with means consisting, i room-conditioningunit 2, itself adapted, and so controlled by a room thermostat 3 as tocarry out the method described and explained in my I is equipped thisinstance, of av United States Letters Patent No. 1,913,681. kIt is to benoted, however, that whereas it has heretofore been customary to locatetheroom-conditioning unit on an outside wall of the room, and to takethe required fresh air supply directly from outdoors through an openingin the wall, it will usually be found expedient, in the presentinstance, to locate the unit on an inner partition adjacent an immuredbranch conduit 4 adapted to supply preconditioned air. But, as will beunderstood by those skilled in the art, the location of theroom-conditioning unit and the arrangement of the preconditioned airconduits will vary with circumstances and with the particular form ofapparatus used.

Room-conditioning units of various constructions may be utilized tocarry out the method, one suitable construction being shown in Figure 2.In this case, theunit consists of a suitable cabinet 5 adapted to be seton the floor, against a wall of the room served, this cabinet beingprovided with a fresh air inlet 6, a recirculating air inlet 'I and anair discharge outlet 8, The branch conduit 4 is connected to the freshair inlet 6 to supply preconditioned air in the volumes required and ata sufciently low temperature to take care of the maximum cooling duty.The recirculated air inlet 1 and the communicate with the room or spaceserved. It is preferred that these communicate with the discharge outlet8 room directly, or as freely as possible, and that the outlet 8 bearranged to deliver the air into the room in the form of a substantiallyvertical jet with suihcient force to carry to the ceiling.

.The cabinet contains a motor driven fan 9, for drawing air through theinlets and discharging it through the outlet. The cabinet is alsoequipped with a radiator I0 for heating the air drawn through it, andwith a filter II for cleaning the air. The arrangement is such that onlythe air drawn through the recirculation air inlet 7 is heated, but allof the air is filtered. However, it is to be understood that filtrationis not essential to the method. Dampers I2 and I3 regulate the flow ofair through the inlets 6 and 1, respectively, and are so linked togetherthat one closes as the other'opens its associated air passage. A valve(not shown) controls the flow of steam to the radiator. The thermostat 3controls the operation of the dampers I2 and I3 together with theradiator valve, in a manner and through mechanism well known in the art,so that on a rising room temperature within'a selected range the freshair damper I2 is held closed (or to a fixed minimum setting), and therecirculated air damper I3 is held opened while the radiator controlvalve is gradually throttled through the lower portion of said range,after which the fresh air damper is gradually opened while therecirculated air damper isA correspondingly closed.- On a falling roomtemperature within said range, the operation is reversed. Of course, ineither phase of the cycle, the room temperature, and hence the controlmechanism, comes to rest whenever equilibrium is established betweenduty and output. As explained in Patent No. 1,913,681, certainmodifications of the above-described cycle of control may be employed,but this will suice to illustrate the principle of the method thereof.

The effect of the patent method is to maintain an approximately uniformtemperature in the room under varying weather conditions and the effectso f occupancy. In cold weather, the heat gains due to occupancy,sunshine, etc., are usually more than offset by heat losses through theouter walls, hence, the room temperature tends to fall and will bebrought to rest at some point within the lower portion of the controlrange, where the fresh air supply is reduced to a minimum and theradiator control valve is open to supply enough heat to make up thedeficit between the natural gains and losses. On the other hand, whenconditions are such that the natural gains exceed the losses, the -roomtemperature would tend to rise and must be brought to rest in the upperportion of the control range, where the radiator control valve is shutand the dampers I2 and I3l are adjusted to recirculate less air andadmit enough fresh air to neutralize the excess heat gain.

Notwithstanding outdoor primary factor in determining the duty on thesystem, it is not controlling. In many instances occupancy and sunshineimpose a substantial cooling duty in comparatively cold weather.vThroughout a large portion of the year, circumstances permit of a widerange in cooling duty, and hence, in the quantity'of fresh air required.Where this air is drawn directly from outdoors by the room-conditioningunit 2, no problem is involved in connection with the supply. But, Wherethe supply must be drawn in Varying amounts from a limited source suchas a separate preconditioning station,`a problem is introducedtemperature is the damper size lof the units,

` drawsi'ts supply of air froms 'ageI1.- -The preconditioning chamber-I6, which 'may be of any suitable form-'and construction is pro'- videdwith a heating element iii-regulating the available supply according tothe demand. The present -invention is directed 'to a solution of thisproblem.

In certain instances it is feasible to equip each individualroom-conditioning unit with additional preconditioning means, thusavoiding the problem cited, but in other cases it is not practicable,and it is rarely as satisfactory as protioning purposes, particularlywhere this involves precooling. The mere addition of a cooling coil inthe type of room-conditioning unit shown in Figure 2 would not' beespecially diflicult. As a l matter of fact, the same radiator could bemade to serve for either heating or cooling by employing water as acirculating medium and heating or cooling the'water as required;However, the

adaptation of apparatus of this character to summer service is not so.simply accomplished.. A study of the regulating mechanism will indicatethat it is not suitable for a radiator functioning in a coolingcapacity. In order therefore to adapt room-conditioning units of thetype required to carry' out the aforesaid method in summer service, itwould be necessary to locate the precooling coil outside the portcontrolled by the I2 and provide additional thermo- Static regulation.4In addition to greatly increasing the cost, this would-materiallyincrease the unitsfor double service is complicated, unsightly andcostly. Moreover, artificial cooling involves dehumidication, andfthisbr'ngs up a'sanitarydrainage problem vthat is not easily disposed'of.

4Thepresent invention provides -an arrangement'wherein the simple unitsystem of my which is'itself often objectionother closes.

earlier patent, with its manifold advantages, is

used for conditioningrthe rooms themselves, while a central plant isemployed to properly .prepare or precondition the air supplied, as'vrequired, to the room-conditioningunitsl In other words, the amount offresh air required and circulated 'by the room-'conditioning units 2,while the Aaggregate amount pared and distributed asrequired, by acentraliA demanded is prepreconditionin'g plant. Referring again to-Fig- -electric motor or other chamber I 6` through` "a suction conduitorpas- I8 and/or cooling.

is forcdjby a-fan` or blower |5. The fan 'is,^of course, driven by an`suitablemeans and..

a preconditioning to maintain an op-y vtimum"condition in'each room,Aunder varying ,Weather andoccupancy conditions,.is. regulated u re -1,each roem-conditioning .unit 2 is supplied' AIl -from a trunk w I4 intoand through ment 2l while the required air supply flows into thepreconditioning chamber through the intake duct or passage 22 whichcommunicates with the receiving compartment 20 and is arranged to toregulate the ow from the two sources as desired.

Wherejair is taken from within the building,

l it should preferably bedrawn from some quarter, such as a maincorridor,'which is not itself equipped with conditioning units 2 butinto which air from the rooms' so equipped may overflow, either throughsuitable vents or by` leakage. In such cases, the complete circulationprocess may be facilitated by either allowing about an inch clearanceunder doors between such roomsand the corridors, or, by providing ventsin the lower rails of the doors or in the corridor partition. .Anarrangement which has been found satisfactory is shown in Figure 1,wherein the room I -is vented into the corridors through an oifset vent26 which communicates at its lowermost end with the room at a point nearthe floor and at its uppermost end with the upper region of thecorridor.

The air supplied to the preconditioning chambers should never be drawnwholly from within the building except when the rooms are unoccupied,unless the outdoor temperature is higher than that to be maintained inthe delivery'compartment 2I. When the outdoor temperature is lower. thanthat to be maintained in the delivery compartment, only enough airshould be drawn from outdoors-to allow the temperature of the mixture tobe at or below that to be maintained in the delivery compartment. Toprovide for this,4 the dampers 24 and 25 may be linked up to operate inunison so that as one opens the These dampers may be controlled by'athermostat 21 so as to maintain a lixed temperature in the receivingcompartment 20, which will be at or below that maintained in thedelivery compartment 2I lsc long as the outdoor temperature is belowthat point and the-indoor supply source temperature is above it. Thiswill insure that only so much raw air will be used in cold weather-asmay be required to provide for proper ventilation of the rooms; and,that during warming up periods, when the building is itself cold,I allair will be recirculated.

The abovedescribed arrangement should 'be vsuch that -the thermos'taticcontrol' mechanism,

21 operates against a spring 23' or other force tending tot hold theoutdoor damper 24 closed and the indoorsupplydamper 25 openaconventional .arrangement well understood in the art. Said-thermostatmechanism 21 in response to'air temperature conditions -in `thereceiving compartment-2J), normally functions within a Aselectedtemperature range, when theternperatureis rising through that range, togradually open the damper 24` and correspondingly close element I9 whichserve Ato subdividev the chamber 'f fanis communicates with the deiiverycomparifinto a receiving compartment 20.' anda delivery -The. suctionpassage -I 1 tothe the damper 25 against thetension` ofthe spring 23'.Alternatively, when the temperature in the `receiving compartment 20isfalling, within the selected temperature' range, said thermostatmechanism 21 operates toallow said spring'23 to gradually close thedamper 24 and correspondingly op'en the damper 25. ySo long as the ternperature in the receivingl compartment 20 remains "constant Vatisomepoint within the se-V 4- lected control range, the thermostat 2'I actsto maintain `the dampers 24 and 25 in whatever intermediate position thedampers may be.

A leakstat or similar limiting device 2,8 responsive to tion at a pointrepresentative of the indoor supply source temperature, is utilized torender the thermostat 21 ineffective and allow the outdoor damper 24 toclose and the indoor damper 25 to open whenever the outdoor temperatureexceeds that at the indoor supply source. the refrigeration load will bekept to a minimum.

The air-heating element I8 and the air-cooling element I9 are indicateddiagrammatically and may be'of various forms well known in the art. Forthe purpose of explaining the invention, it will be1 assumed that theheating element I8 consists of the usual steam radiator and that` thecooling element I9 is a radiator or coil adapted to the use of asuitab-le refrigerating agent, such as ammonia, freon, etc. It will alsobe further assumed that the necessary equipment is provided to renderthese elements serviceablel in their respective capacities, all of whichis well understood in the art. It will be understood that both elementsare only necessary for yearround service, and, that either may beomitted or the two functions combined in one element without affectingthe broader phases of the invention.- On the other hand, humidiers,lters, ozonators or other preconditioning devices may be added, ifdesired.

Valves 29 and 30 or other suitable means are provided to control therespective heating and cooling elements. 'I'hese valves may be regulatedthrough suitable thermostatic means 3l placed in the deliverycompartment 2I or other appropriate point to maintain a limited range oftemperature of the preconditioned air. For example, with the pneumaticsystem of control, an intermediate, direct-acting thermostat 3I- may beused to control a direct-acting steam valve 29 and a reverse-actingrefrigerant valve 30 so that, at the lower limit of the control rangethe steam valve will be wide open while the refrigerant valve will beclosed; and so that, as the temperature of rises above said lower limit,the steam valve will gradually close up to some selected point withinthe range where it will be fully closed; and so that when thetemperature of the preconditioned air exceeds said selected point,either critically or by some arbitrary margin, the refrigerant valvewill gradually open until the temperature rise is halted.

A by-pass duct or passage 32 affords communication between the airpassages on the suction and delivery sides of the fan.

In the arrangement shown, which is commonly known as a draw-througharrangement for theY reason thatthe air is drawn rather than forcedthrough the preconditioning chamber, the by-pass is preferably connectedbetween the trunk duct I4 and the .receiving compartment 20. As will beunderstood by those skilled in the art, a so-called blow-througharrangement might be substituted, wherein the intake duct 22 wouldconnect with the suction inlet of the fan I5 instead of with thereceiving compartment 20, the suction duct I1-in this case being omittedand the fan arranged to discharge into the receiving compartment. Withsuch an arrangement, the trunk duct I4 would merely become an extensionof the delivery compartment 2I or it might be omitted, and the branchducts outdoor temperature and set to func- In this way,v

the preconditioned airv 4 extended separately from the deliverycompartment. In the latter case, the by-pass 32 will connect the intakepassage 22 with the trunk duct I4 or delivery compartment 2I.

The by-pass 32 is preferably provided with a damper 33 which may beregulated so as to maintain a uniform pressure in-the trunk duct I4through the agency of a static pressure regulator 34. Under a maximumdemand for preconditioned air to supply the various room-conditioningunits 2, the regulator will close the damper; but, as the demand fallsoff the static pressure will tend to rise and cause the regulator togradually open the damper 33 until the tendency ceases. In this way, aconstant pressure of properly preconditioned air is made available tomeet the varying demands of the room-conditioning units at all times.The pressure regulator 34 and even thedamper 33 may be omitted withfairly satisfactory results where the distributing system is not toocomplicated and is well proportioned; but, in such cases, the by-pass 32should be taken from a point near the far end of the trunk duct I4. Theby-pass need not be the full size of the trunk duct, but should be largeenough to handle the difference between the maximum and minimum supplyof preconditioned yair required at various times by the roomconditioners.

Ordinarily, the maximum supply of preconditioned air required to servethe various room conditioners will be considerably less than theaggregrate peak demands of same, and should be independently estimatedon the basis of the actual maximum demand of the group at any one time.For example, the requirements of the units serving e'ast rooms will begreatest in the morning, whereas those of units serving West rooms willbe greatest in the afternoon. In a building exposed alike on oppositesides, the load factor may be as little as half the required maximumoutput of the individual units collectively.

It is evident that with the arrangement described, a uniform temperatureof preconditioned air is made available in the quantities demanded tomaintain optimum conditions inthe various rooms the year around. Theentire system operates automatically to this end without furtherattention than such adjustment of the room thermostatsas may be requiredat different seasons, and to maintain a proper supply of steam inweather when it is necessary. As is well understood in the art, therefrigeration equipment may be arranged to operate automatically inresponse to the demand. Ordinarily, a temperature of about -55 in thetrunk duct I4 will -serve this purpose best. The optimum roomtemperature. for occupants customarily clothed and, sedentarily engagedwill vary from about iT-'72 in winter, to 7880 in summer.

It is, of course, to be understood that although I have describedv indetail a preferredembodiment of my invention, the invention is not to bethus limited, but only insofar as defined by the scope and spirit of theappended claims.

I claim as my invention:

1. Air conditioning apparatus comprising a -housing having an outlet forconditioned air and separate intakes for air from an outdoor and anindoor source respectively, a damper for each of said intakes, meansnormally biasing one of said dampers to closed position and the other toopen position, mechanism for operating said dampers in unison so as toclose one while opening the other, thermal air-conditioning meansthermostatic of said thermal air-conditioning means for actuwithin saidhousing, means for moving air through said housing from said intakespast said thermal air-conditioning means to said outlet, means withinsaid housing ahead ating said damper operating mechanism, temperatureresponsive meansin the outdoor intake operable to render saidthermostatic means ineffective when the temperature of the air in theoutdoor intake exceeds that in the indoor intake', a by-pass from saidoutlet to said housing ahead of said thermal air-conditioning means, adamper in said by-pass and pressure responsive means in said outlet forcontrolling said by-pass damper to maintain a substantially` uniform airpressure at said outlet irrespective of the demand for conditioned airfrom said outlet.

2. 'I'he method of thermally conditioning air,

which comprises moving air along a confined path providing intakes intosaid path from a source of indoor air and from a source of outdoor air,thermally conditioning the intaken air at a point along said connedpath, controlling the selection of the source and of the proportionateVolumes of air taken in from said sources in accordance with therelative temperatures of the outside air and of the intaken air at aposition ahead of said point of thermal conditioning but. beyond thepoints of intake, advancing said conditioned air under a pressure headfor delivery and by-passing any excess. of such conditioned air overdelivery demand back to said conned path ahead of said point of thermalconditioning so as to maintain said pressure head substantiallyconstant.

GERALD E. OTIS.

